This application incorporates by reference Taiwanese application Serial No. 090120154, Filed Aug. 16, 2001.
1. Field of the Invention
The invention relates to a tracking location adjustment method in an optical storage device, and more particularly to a tracking location adjustment method according to a Tracking Error (TE) signal and a Radio Frequency Ripple (RFRP) signal in an optical storage device.
2. Description of Related Art
FIG. 1 schematically illustrates a structure of a general optical storage device. The optical storage device could be a Compact Disk-Read Only Memory drive (CD-ROM drive) or a Digital Versatile Disk drive (DVD drive) or the like. In FIG. 1, a spindle motor 100 rotates a disc 101 at a required speed. A sled driving motor 102 is for driving a sled 105 having an optical pickup head 104 to proceed rough tunings, for example track-jumping and seeking operations. The disc 101 has multiple tracks 103 for recording data. So, in a seeking operation, the optical pickup head 104 is moved to the desired track for reading information. In addition, there are fine tuning operations including for example, focusing and tracking. In a focusing operation, the lens 120 is moved vertically and reads the information on the disc 101 correctly. In a tracking operation, the lens 120 follows the desired track horizontally. Afterward, a laser beam is emitted on the disc 101, and then the optical sensor on the optical pickup head can receive analog signal reflected from the disc 101.
A pre-amplifier 106 synthesizes signals, which are obtained through the optical pickup head, into the Radio Frequency (RF) signal and other necessary signals for different servo controls, such as the Tracking Error (TE) signal and the Radio Frequency Ripple (RFRP) signal, and so on. The RF signal is also transmitted to a control circuit 108 including a Digital Signal Processor (DSP), and other analogue or digital circuits. The RF signal is corrected and interpreted by the control circuit 108 into data, then transmitted to a decoder 112. Then, the output from the decoder 112 is transmitted to a host computer 114 for further process. On the other hand, the control circuit 108 also transmits servo signals to power amplifiers 116 and 118 for activating the spindle motor 100, the sled motor 102, the focusing actuator of the lens 120 on the optical pickup head 104, and a tracking actuator. In addition, a microprocessor 122 is in charge of the whole processing control of the optical storage device and user interfaces, such as opening of the disc tray and so on.
The optical pickup head 104 reads the data on the disc 101 by emitting three beams: a main beam, and two sub-beams at the same time, and then decodes reflected signals. The reflected signal related to by the main beam is defined as the RF signal, the reflected signal related to one sub-beam is defined as the signal E, and the reflected signal related to the other sub-beam is defined as the signal F. The two sub-beams are separately located on both sides of the main beam. The distance between the two sub-beams is xc2xd of the beam""s wavelength. So, the phase difference between the two sub-beams is 180 degree. FIG. 2 is a timing diagram of signals in an optical storage device. When the main beam focuses on a track, the amplitude of the RF signal is maximum. When the main beam focuses between tracks, the amplitude of the RF signal is minimum. The difference between the upper envelope and the lower envelope of the RF signal is defined the RFPR signal. Or, the filtered RF signal via a low-pass filter is also defined as the RFRP signal. The TE signal is defined as the difference between the value of the signal E and the signal F. At the timing point T2, the value of TE signal is 0, which means the main beam is focused on a track center. However, the value of signal TE is also 0 if the main beam focuses between tracks, such as at the timing point T4. When the lens is located at the edge of tracks, the absolute value of TE signal is maximum, such as at the timing point T1 and T3.
Therefore, a complete cycle of signal TE or signal RF means the optical pickup head passes through one track. The tracking ability of an optical storage device can influence the quality and precision of reading data on a disc. Traditionally, the zero-crossing point of TE signal is used to identify if a tracking process has been done. However, the phase difference between the signal E and the signal F is not ideally 180 degrees. The possible error of the phase difference can reach 45 degrees. For this reason, it will cause incorrect tracking location and poor quality of signal reading if the tracking location is decided only according to zero-crossing point of the TE signal.
It is therefore an objective of the invention to provide a method of tracking location adjustment in an optical storage device.
In accordance with the foregoing objective and other objectives of the invention, the invention provides a method of tracking location adjustment in an optical storage device for finely moving an optical pickup head to track on an adjusted tracking location. The method is illustrated as follows. Firstly, the optical pickup head reaches the first tracking location according to a tracking error (TE) signal. Secondly, the optical pickup head is finely moved to an adjusted tracking location where the value of the amplitude of RFRP signal is maximum. The method can avoid wrong tracking location by simply based on the TE signal, then enable the optical pickup head to reach the correct track center and improve the quality of data reading.
The invention can be more fully understood by reading the following detailed description of the preferred embodiments, with reference made to the accompanying drawings.